Clarification on Disk-Only Snapshots in Apache CloudStack 4.20 - KVM Hypervisors

["P, Rajasekar" <Ra...@netapp.com.INVALID>]

Hello Apache CloudStack Community,

I am currently using Apache CloudStack version 4.20 and have a question regarding snapshot functionality and disk format limitations.

Specifically, I would like to know if it is possible to perform disk-only snapshots for all possible disk formats (example qcow2 ad raw) and storage protocols (Ex NFS, NVME over TCP and FC).

According to the CloudStack usage guide, instance snapshots are supported only for KVM (NFS) using the QCOW2 format.

Here, I want to understand, if there are any limitations of cloud stack - kvm snapshots, with respect to the disk format and storage protocols.

Thank you for your assistance.

Best regards,
Raj.

Re: Clarification on Disk-Only Snapshots in Apache CloudStack 4.20 - KVM Hypervisors

[João Jandre Paraquetti <jo...@scclouds.com.br>]

Hello, Raj

It is unclear to me if you are asking about volume snapshots, or VM 
disk-only snapshots. Thus, I'll explain both :)

Please note that I am mainly talking about the native/open source 
integrations, I am not aware of how these operate for 3rd party 
integrations such as Linstor, PowerFlex and StorPool.

### Volume snapshots

In 4.20, using KVM, volume snapshots are supported with both QCOW2 and 
raw types:
- QCOW2 may be used with NFS, shared-mount-point (e.g. iSCSi/FC with 
GlusterFS/OCFS2), or local storage.
- Raw images are supported when using RBD (Ceph).

These snapshots are always full snapshots. From 4.21 onward, when using 
QCOW2 and file-based storage (NFS, shared-mount-point, local storage), 
incremental snapshots will be supported.

### VM disk-only snapshots

Support for disk-only VM snapshots is the same as volume snapshots. The 
current implementation will use the same workflow as volume snapshots. I 
have some gripes with it and thus have proposed a new implementation 
that supports file-based storage and is also incremental. But it has 
still not been approved by the community: 
https://github.com/apache/cloudstack/pull/10632

Dear community, if I have missed a storage/volume type that supports 
snapshots, please amend my explanation :)

Best regards,

João Jandre.

On 5/15/25 11:59, P, Rajasekar wrote:
> Hello Apache CloudStack Community,
>
> I am currently using Apache CloudStack version 4.20 and have a question regarding snapshot functionality and disk format limitations.
>
> Specifically, I would like to know if it is possible to perform disk-only snapshots for all possible disk formats (example qcow2 ad raw) and storage protocols (Ex NFS, NVME over TCP and FC).
>
> According to the CloudStack usage guide, instance snapshots are supported only for KVM (NFS) using the QCOW2 format.
>
> Here, I want to understand, if there are any limitations of cloud stack - kvm snapshots, with respect to the disk format and storage protocols.
>
> Thank you for your assistance.
>
> Best regards,
> Raj.
>
>